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mm/khugepaged: fix GUP-fast interaction by sending IPI
commit2ba99c5e08
upstream. Since commit70cbc3cc78
("mm: gup: fix the fast GUP race against THP collapse"), the lockless_pages_from_mm() fastpath rechecks the pmd_t to ensure that the page table was not removed by khugepaged in between. However, lockless_pages_from_mm() still requires that the page table is not concurrently freed. Fix it by sending IPIs (if the architecture uses semi-RCU-style page table freeing) before freeing/reusing page tables. Link: https://lkml.kernel.org/r/20221129154730.2274278-2-jannh@google.com Link: https://lkml.kernel.org/r/20221128180252.1684965-2-jannh@google.com Link: https://lkml.kernel.org/r/20221125213714.4115729-2-jannh@google.com Fixes:ba76149f47
("thp: khugepaged") Signed-off-by: Jann Horn <jannh@google.com> Reviewed-by: Yang Shi <shy828301@gmail.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Peter Xu <peterx@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> [backported, no changes necessary] Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
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3 changed files with 7 additions and 3 deletions
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@ -222,12 +222,16 @@ extern void tlb_remove_table(struct mmu_gather *tlb, void *table);
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#define tlb_needs_table_invalidate() (true)
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#endif
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void tlb_remove_table_sync_one(void);
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#else
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#ifdef tlb_needs_table_invalidate
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#error tlb_needs_table_invalidate() requires MMU_GATHER_RCU_TABLE_FREE
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#endif
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static inline void tlb_remove_table_sync_one(void) { }
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#endif /* CONFIG_MMU_GATHER_RCU_TABLE_FREE */
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@ -1093,6 +1093,7 @@ static void collapse_huge_page(struct mm_struct *mm,
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_pmd = pmdp_collapse_flush(vma, address, pmd);
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spin_unlock(pmd_ptl);
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mmu_notifier_invalidate_range_end(&range);
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tlb_remove_table_sync_one();
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spin_lock(pte_ptl);
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isolated = __collapse_huge_page_isolate(vma, address, pte,
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@ -1391,6 +1392,7 @@ static void collapse_and_free_pmd(struct mm_struct *mm, struct vm_area_struct *v
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lockdep_assert_held_write(&vma->anon_vma->root->rwsem);
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pmd = pmdp_collapse_flush(vma, addr, pmdp);
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tlb_remove_table_sync_one();
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mm_dec_nr_ptes(mm);
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page_table_check_pte_clear_range(mm, addr, pmd);
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pte_free(mm, pmd_pgtable(pmd));
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@ -152,7 +152,7 @@ static void tlb_remove_table_smp_sync(void *arg)
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/* Simply deliver the interrupt */
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}
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static void tlb_remove_table_sync_one(void)
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void tlb_remove_table_sync_one(void)
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{
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/*
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* This isn't an RCU grace period and hence the page-tables cannot be
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@ -176,8 +176,6 @@ static void tlb_remove_table_free(struct mmu_table_batch *batch)
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#else /* !CONFIG_MMU_GATHER_RCU_TABLE_FREE */
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static void tlb_remove_table_sync_one(void) { }
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static void tlb_remove_table_free(struct mmu_table_batch *batch)
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{
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__tlb_remove_table_free(batch);
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